Comparative Effects of Half-Length Coded Wire Tagging and Ventral Fin Removal on Survival and Size of Pink Salmon Fry

Abstract

The survival and adult size of pink salmon Oncorhynchus gorbuscha marked as recently emigrating fry with coded wire tags (CWTs) were compared with those of sibling groups that were either unmarked or marked by removing a ventral (pelvic) fin. Prerelease mortality was significantly higher for coded-wire-tagged fish. Survival from fry release to adult return was equal to or less than that of fish with ventral fin clips. Pink salmon marked with CWTs were similar in size at return to pink salmon with ventral fin clips but significantly smaller than unmarked fish. These results indicate that reduced growth after marking contributes to the lower survival reported in other studies of pink salmon marked with CWTs or fin clips. Marking pink salmon as recently emigrating fry with CWTs provides a powerful tool for differentiating between a large number of treatment groups and categories, but doing so will affect survival and size at return and is more detrimental to survival than ventral fin removal.